This invention relates to sheet material cutters, such as cloth cutters, having a table for supporting the material to be cut and wherein vacuum is applied to at least a portion of the support surface to compress the material as it is cut, and/or to aid in holding the material to the support surface, and deals more particularly with a system for supplying vacuum to such a cutting table in the case where the table is movable over a horizontal floor between a number of different cutting stations.
It is known, for example from U.S. Pat. No. 3,790,154, to provide the cutting table of a sheet material cutter with a vacuum which is applied to the material supporting surface at least in the vicinity of the cutting tool to compact and hold in place the material being cut, the vacuum generally working in cooperation with a sheet of thin plastic or similar air impermeable material spread over the material to be cut. It is also known, for example from U.S. Pat. Nos. 4,345,496, 4,646,911 and 4,476,756 to make the table of such a cutter in such a way that the support surface for the material to be cut is provided by an endless conveyor so that the material to be cut may be first spread on a separate spreading or lay-up table to form a lay-up consisting of a number of layers of material and may then be moved from the spreading table to the cutter through the conveying action of the cutting table's endless conveyor. It is also known, in a sheet material cutting plant, to provide a number of spreading tables serviced by a single cutter movable relative to the spreading tables to bring it into a position of cooperation with any selected one of the spreading tables. Thus, in the latter situation, while the cutter cooperates with one spreading table to receive and cut the layout made available at that table spreading may take place at one or more of the remaining tables to form one or more new lay-ups for later cutting by the cutter.
In known cutters of the type intended for movement between a number of spreading tables, the vacuum needed for application to the material support surface has been provided by a vacuum pump and drive motor carried by the frame of the cutter table so as to be part of the table and movable with it between its various cutting stations. Such movable cutting tables with built-in vacuum sources have a number of disadvantages including the fact that a relatively large amount of electrical power has to be supplied to the drive motor through some sort of connection permitting movement of the table, the fact that a relatively high degree of noise is produced in the vicinity of the cutting table by the running of the motor and the pump and the exhaust of air from the pump, and the fact that the flow of air through the vacuum system may have an adverse effect on the heating or air conditioning of the room containing the cutter, which effect is difficult to control because of the moving nature of the vacuum pump. Another disadvantage is that different cutting applications using the same general cutting table may require quite different amounts of vacuum power, yet it is difficult for the manufacturer of cutters with built-in vacuum sources to make such tables available with a wide selection of different built-in vacuum sources to precisely match the needs of different applications. In other words, it may be practical for the manufacturer to make available cutters with only one standard vacuum source, or with a very limited selection of standard vacuum sources, which may provide a much higher maximum vacuum power than needed for the application in question.
The general object of this invention is therefore to provide a system for supplying vacuum to a movable sheet material cutter which overcomes the above described disadvantages of movable cutters with built-in vacuum sources.
Other objects and advantages of the invention will be apparent from the following detailed description of a preferred embodiment.